The present invention relates to an image printing apparatus, and more particularly to an image printing apparatus in which the inflow of impure matters via the developer carrier roller can be avoided effectively.
Relating to FIG. 1, the conventional image printing apparatus basically comprises two pivotally detachable sections, i.e, an upper main body 1 and a lower main body 1'. A drum 2 is provided in upper main body 1, and an electrifying apparatus 3 for supplying constant charges to the surface of drum 2 is provided on one side of drum 2. A light exposure apparatus 4 for forming an electrostatic latent image on drum 2 by generating local photocurrent corresponding to the image printing signal, is provided next to electrifying apparatus 3. Also, developing apparatus 5 for developing the electrostatic latent image into a visible image by attaching only toner 5f except for carrier 5g to drum 2 on which the electrostatic latent image has been formed by light exposure apparatus 4, is located in the lower section of drum 2, that is, inside lower main body 1'. In addition, an image-transferring apparatus 6 for transferring the developed electrostatic latent image onto a printing paper P is located opposing drum 2 and on the other side of drum 2. A cleaning apparatus 7 for cleaning toner 5f remaining after printing the image is located in the upper section of drum 2, that is, inside upper main body 1. On the other hand, printing paper P onto which the electrostatic latent image is being transferred, is drawn from printing paper dispensing cassette 8 and moved up to the exact transferring position by paper guide plate 9.
In developing apparatus 5, a hopper roller 5e is provided to furnish toner 5f to the supplying roller 5d which is located next to the hopper roller 5e. The hopper roller 5e also plays the role of toner freezing prevention. Next to the supplying roller 5d is located a developer stirring roller 5c for electrifying the supplied toner by way of creating friction with the carrier 5g. Here, the electrified toner adheres to the carrier to thereby form developer which is then conveyed to the developer carrier roller 5a located between developer stirring roller 5c and drum 2. Keeping a certain small gap from the upper surface of the developer carrier roller, a developer regulating plate 5b is provided to regulate the thickness of the supplied developer on the surface of developer carrier roller 5a. At this time, said developing apparatus 5 can be combined with or separated from lower main body 1' of the apparatus.
In the conventional image printing apparatus as detailed above, printing paper P drawn from a printing paper-dispensing cassette 8 and guided by a paper guiding plate 9 passes the surface of drum 2. At the same time, image transferring apparatus 6 transfers the image of the developed electrostatic latent image having been formed on the surface of drum 2 to printing paper P.
However, in the conventional image printing apparatus, the developer carrier roller of developing apparatus is exposed to the outside when the upper main body is pivotally detached from the lower main body, so that foreign particles may thereby enter the apparatus and a user may be polluted with the toner. These foreign particles then become mixed into the developer and inserted between the developer carrier roller and the developer regulating plate to cause the layers of the developer non-uniform, which then causes the undeveloped image such as white lines, etc. in the transferred image on printing paper. Moreover, an additional printing paper guiding plate is necessary for guiding the printing paper to the drum, which results in the unfavorable enlargement of the apparatus and increased installation space, as well as increased manufacturing costs.